Fig. 6

Transgenic over-induction of astrocytic CCL2 in MPTP mice increases nigral CCR2⁺ monocyte infiltration and loss of DA neurons. a–b Use of transgenic GFAP-CCL2 mice to enhance MPTP-mediated astrocytic CCL2 induction. Immunohistochemistry with anti-GFP antibodies (brown) shows increased presence of CCR2-GFP⁺ cells (arrows) within the MPTP-affected SNpc of GFAP-CCL2/CCR2-GFP double-transgenic mice (b) as compared to CCR2-GFP single-transgenic littermates (a) (measured at 24 h after MPTP intoxication; insets show enlargements). (Scale bars; b, 200 μm; inset in b, 10 μm). c Quantification of presence of CCR2-GFP⁺ cells within the SNpc (24 h after MPTP intoxication) between GFAP-CCL2/CCR2-GFP mice (n = 6) and CCR2-GFP littermates (n = 4), suggests that enhancing MPTP-mediated astrocytic CCL2 induction increases nigral CCR2⁺ monocyte infiltration (by 2.7 fold, **P < 0.01, Dunn’s test). Counts represent the estimated total of CCR2-GFP⁺ cells within the entire SNpc (individual mice are shown; red bars, mean). d MPTP-induced DA neuronal loss in GFAP-CCL2 mice and wild-type non-transgenic littermates. Quantification at 7 (n = 12) and 14 days (n = 10) after MPTP intoxication, shows robust and stable loss of DA neurons in wild-type mice (26 and 29%, respectively, compared to saline injected controls (n = 5); ***P < 0.001, ANOVA with Holm-Sidak test). While saline injected control GFAP-CCL2 mice (n = 4) have normal numbers of DA neurons, the MPTP-induced DA neuronal loss compared to wild-type mice is significantly increased in GFAP-CCL2 transgenic mice (*P = 0.01, ANOVA with Holm-Sidak test), both at 7 (n = 10) and 14 days (n = 12) after MPTP intoxication (37 and 40%, respectively, compared to saline injected controls (n = 4); ***P < 0.001, ANOVA with Holm-Sidak test). Counts represent the estimated total of TH⁺ DA neurons within the entire SNpc, 7 and 14 days after acute MPTP intoxication (individual mice are shown; red bars, mean)